Suction pipes for use in pumping liquid from containers



Dec. 14, 1965 SUCTION PIPES FOR USE IN PUMPING LIQUID FROM CONTAINERS Filed 001;. 31, 1963 I nuen for Wu 4 MM Gmwm (0mm fmdm Attorney w. G. COWAN 3,223,039

United States Patent Ofiice 3,223,039 Patented Dec. 14, 1965 3,223,039 SUTI N lPlPES FQR USE IN PUMPING LEQUED FR Uh/i' C(DNTAINERS Wiliiam Graham Cowan, East Kilbride, Scotland, assignor to J. H. Carruthers 8; Company Limited, East Kilhride, Scotland, 21 British company Filed Get. 31, 1963, Ser. No. 320,480 Claims priority, application Great Britain, Nov. 1, 1962, 41,288/62 7 (Iiairns. (Ci. 103-2) This invention relates to suction pipes for use in pumping liquid from containers.

For pumping efliciency the annular bottom entry between the bottom of the suction pipe and the container bottom must be large in order to avoid undue friction when the pump is operating at full capacity. On the other hand, the enlargement of said annular bottom entry creates disadvantages as follows:

(1) An increase in the distance between the bottom of the suction pipe and the container bottom would result in a considerable quantity of liquid being left in the container.

(2) An increase in the diameter of the bottom of the suction pipe would result in an increase in bulk and cost and, moreover, in the event that the container is a tank on a marine tanker, any list in the vessel during discharge of the tank would tend to cause part exposure of the entry opening and consequent loss of suction.

The problem of striking a compromise between the different requirements becomes acute when the pump and suction pipe are large, the liquid is viscous, and the quantity of residual liquid in the tank must be a minimum, as for instance when oil is being pumped from a marine tanker.

The object of the present invention is to provide a simple, compact and etficient suction intake device which enables high-efiiciency pumping through the suction pipe throughout the entire discharge period without the disadvantages associated with enlargement of the annular bottom entry.

According to the present invention, a suction intake device for use in pumping liquid from a container com prises a standpipe, an entry at the bottom of the standpipe, entry means above said bottom entry, and floatvalve means operable by the liquid in the container to close said entry means against the atmosphere when the liquid level falls; wherein the upper entry means is an annular entry located adjacent to the bottom entry and surrounding the standpipe so that a large and constant area for entry of liquid to the standpipe is available throughout a major portion of the period required to empty the container of liquid, and the float-valve means consists of an annular seat at the annular upper entry and a buoyant ring surrounding the standpipe and vertically reciprocable into and out of engagement with the seat.

By virtue of the invention, the bottom entry of the standpipe may be a relatively narrow annular entry of relatively small diameter without affecting the pumping efliciency, as the pump can be operated efliciently at full capacity over a major portion of the discharge period, that is when pumping through both entries, and at reduced capacity over the remaining portion, that is when pumping through the bottom entry only.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawing which is a side view of a suction intake device, partly in suction, forming the bottom portion of a suction standpipe in the oil tank of a marine oil tanker.

Referring to the drawing, a main cylindrical stand pipe 1A extends downwards within an oil tank 2 and is connected at its upper end to a variable-delivery centrifugal pump 3 to empty the tank of oil. The bottom of the standpipe 1A has mounted thereon a suction intake device 4 which comprises a short standpipe forming a downward extension of the standpipe 1A. The device 4 includes a cylindrical tube 5 secured at its flanged upper end to the flanged lower end of the standpipe 1A. An upper entry in the form of an annular U-duct 6 branches from the bottom of the tube 5, the other limb 8B of the U being secured at its flanged upper end to the flanged lower end of the tube 5. In the U-duct 6 a central cylindrical bore 7 of smaller diameter than that of the tube 5 is spaced below the lower end of the tube 5. The inner imb 8A of the U-duct is sloped to discharge oil upwards and radially inwards so that the oil flow merges smoothly with the oil flow issuing upwards from the bore 7. The outer limb 8B of the U-duct terminates in a concave annular seat 12 adjacent to an annular oil inlet port 9, and a vertically reciprocable buoyant ring 13 surrounding the tube 5 co-operates with the seat 12 to open and close the port 9. The ring 13 consists of a circular section collapsible tubular ring of resiliently compressible material inflated with air to a suitable pressure to render it buoyant. The ring is made of a material resistant to any destructive action of the oil in the tank. For example, a ring suitable for use with the oil is made of nitrile rubber reinforced with Terylene (trademark). The ring 13 is guided in its vertical reciprocation by an exterior peripheral series of axial ribs 14 integral with the tube 5, and upward movement is limited by a horizontal peripheral flange 15 on the tube 5. A tubular inlet member "10 is secured to the bottom of the U-duct 6 to form a continuation of the bore 7, and flares downwards as at 11, terminating about /2 inch above the tank bottom 2 to define therewith a narrow, small-diameter annular bottom entry MA.

A cylindrical coarse-mesh strainer 16 secured at its ends to the outer periphery of the flange 15 and to the outer periphery of the U-duct 6 serves to filter the oil flowing to the port 9, so that the device serves as a strum. A series of say six equispaced radial webs in the U-duct 6, one

being indicated at 17, form in the U-duct a series of upright radial vanes integral with the U-duct walls and adapted to resist the formation in the U-duct of one or more vortices. Feet 18 on the bend 8 of the U-duct 6 rest on upstanding longitudinal members 19 on the bottom of the container 2.

The dimensions of the suction intake device 4 are such that friction losses are nominal when the ring 13 is in closed position and the pump 3 is operating at say 30% maximum. The annular U-duct 6 is designed so that with the ring 13 in open position and the pump 3 operating at maximum capacity there is a flow rate through the U-duct of say 70% capacity with nominal friction losses therein.

The suction intake device operates as follows:

When the liquid level in the container 2 is high i.e. when the suction intake device 4 is fully submerged, the buoyant ring 13 is thrust upwards by the oil against the flange 15 to permit flow simultaneously through the bottom entry 11A and through the upper entry namely the U-duct 6 when the pump 3 is operating at maximum capacity, the flow from the limb 8A merging smoothly with the flow from the bore 7. When the oil level falls below the level at which the ring 13 floats, the ring is permitted to drop on to its seating 12 so that the U-duct is sealed against entry of air. The oil now flows through the bottom entry 11A only, and to avoid excessive loss which would terminate the pumping action, the rate of pumping is reduced. Pumping at reduced rate (say 30% of capacity) is continued until the tank is drained to within /2 inch from its bottom.

The dimensions of the suction intake device, including the difference in level between the port 9 and the bottom entry 11A, may be varied in accordance with different conditions, e.g. differences in the pump or tank or liquid.

The annular U-duct provides a large-area upper entry, and'the buoyant ring surrounding the standpipe provides for fully automatic control of the upper entry with a minimum of moving parts. Also, the buoyant ring tends to be automatically cleaned by the liquid during pumping, and is readily made resistant to attack by solids or corrosive material in the liquid.

Further advantages of the invention are:

(a) A suction intake device of smaller dimensions and less cost than such a device having only one entry.

(b) Greater quantities of liquid can be removed from the tank under conditions of list of the tanker.

(c) A variable delivery centrifugal pump is capable of draining the container to the bottom.

I claim:

1. A suction intake device for use in pumping liquid from a container, comprising a standpipe with a bottom entry, an annular U-duct entry branching from the standpipe above said bottom entry the inner limb of the U- duct being sloped to discharge liquid upwards and radially inwards so that the discharged liquid merges smoothly with the upward flow through the standpipe, an annular seat at the upper end of the outer limb of the U-duct, and a buoyant ring surrouding the standpipe and vertically reciprocable into and out of sealing engagement with the seat so that the pumping proceeds through both the bottom entry and the U-duct entry until the liquid reaches a predetermined low level whereupon the buoyant ring closes the U-duct entry against the atmosphere and pumping continues through the bottom entry alone.

2. The suction intake device according to claim 1, the annular U-duct entry having therein a peripheral series of upright radial webs which tend to resist the formation of vortices in the liquid flowing through the entry.

3. A suction intake device for use in pumping liquid from a container, comprising a standpipe, an entry at the bottom of the standpipe, an annular entry above said bottom entry, an annular concave seat at the annular upper entry, and a buoyant ring of circular section surrounding the standpipe and vertically reciprocable into and out of sealing engagement with the seat so that the pumping proceeds through both entries until the liquid reaches a predetermined low level whereupon the buoyant ring closes the upper entry against the atmosphere and pumping continues through the bottom entry alone.

4. The suction intake device according to claim 3, wherein the buoyant ring is resiliently compressible.

5. The suction intake device according to claim 3,

wherein the buoyant ring in its vertical reciprocation frictionally engages a peripheral series of axial guide ribs on the exterior of the standpipe, and has a topmost position abutting an annular flange on the exterior of the standpipe.

6. A suction intake device for use in pumping liquid from a container, comprising a standpipe, an entry at the bottom of the standpipe, entry means above said bottom entry, and float-valve means operable by the liquid in the container to close said entry means against the atmosphere when the liquid level falls; wherein the upper entry means is an annular entry located adjacent to the bottom entry and surrounding the standpipe so that a large and constant area for entry of liquid to the standpipe is available throughout a major portion of the period required to empty the container of liquid, and the floatvalve means consists of an annular seat at the annular upper entry and a buoyant ring surrounding the standpipe and vertically reciprocable into and out of closing engagement with the seat.

7. A suction intake device for use in pumping liquid from a container, comprising a standpipe, an entry at the bottom of the standpipe, entry means above said bottom entry, and float-valve means operable by the liquid in the container to close said entry means against the atmosphere when the liquid level falls; wherein the upper entry means is an annular entry located adjacent to the bottom entry and surrounding the standpipe to present a large and constant area for liquid entry throughout a major portion of the period required to empty the container of liquid, and the float-valve means consists of an annular seat associated with the annular upper entry and a buoyant resiliently compressible ring surrounding the standpipe and vertically movable into engagement with the seat to accommodate itself yieldingly to the seat and seal the annular upper entry against the atmosphere when the liquid reaches a predetermined low level in the container.

References Cited by the Examiner UNITED STATES PATENTS MARK NEWMAN, Primary Examiner.

LAURENCE V. EFNER, DONLEY I. STOCKING,

Examiners. 

1. A SUCTION INTAKE DEVICE FOR USE IN PUMPING LIQUID FROM A CONTAINER, COMPRISING A STANDPIPE WITH A BOTTOM ENTRY, AN ANNULAR U-DUCT ENTRY BRANCHING FROM THE STANDPIPE ABOVE SAID BOTTOM ENTRY THE INNER LIMB OF THE U-DUCT BEING SLOPED TO DISCHARGE LIQUID UPWARDS AND RADIALLY INWARDS SO THAT THE DISCHARGED LIQUID MERGES SMOOTHLY WITH THE UPWARD FLOW THROUGH THE STANDPIPE, AN ANNULAR SEAT AT THE UPPER FLOW THROUGH THE STANDPIPE, AN ANNULAR A BUOYANT RING SURROUNDING THE STANDPIPE AND VERTICALLY RECIPROCABLE INTO AND OUT OF SEALING ENGAGEMENT WITH THE SEAT SO THAT THE PUMPING PROCEEDS THROUGH BOTH THE BOTTOM ENTRY AND THE U-DUCT ENTRY UNTIL THE LIQUID REACHES A PREDETERMINED LOW LEVEL WHEREUPON THE BUOYANT RING CLOSES THE U-DUCT ENTRY AGAINST THE ATMOSPHERE AND PUMPING CONTINUES THROUGH THE BOTTOM ENTRY ALONG. 